1. Field of the Invention
The invention relates to an undercarpet power wiring system and to an adapter for using existing undercarpet power products in undercarpet wiring systems.
2. Description of the Prior Art
It is commonplace in structures such as office buildings and the like to have electrical power cable routed within the building, in such a manner that the wiring is accessible to the maintenance personnel for installation of different wiring systems, or for the accommodation of new power requirements. Three such methods exist in the field, the first is the undercarpet cable, the second is the elevated floor system, and the third is the poke through system for the concrete floor.
In the first system, the undercarpet cable system, as the name may suggest, uses flat power cable which is routed on the floor of the building and beneath the carpeting; so-called undercarpet power cable. This type of cable power system is advantageous in office buildings where modular offices are likely, and where the relocation of people is commonplace. For example, the electrical power cable is typically run within the walls of the office buildings in a manner typically found in all structures, including homes or residences, with the use of round conductors. However, at the interface of the walls and the floor, a transition to flat undercarpet power cable is made, and the flat cable is actually placed beneath the carpet. In all likelihood, the carpeting is not permanent carpeting as we know it, where the carpeting is tacked to the edges of the walls, but rather is squares of carpeting which are semi-adherent to the floor but yet can be lifted or pulled off of the floor for access to the electrical cabling which rests upon the floor. Such systems are described more fully in U.S. Pat. No. 4,319,075 and U.S. Pat. No. 4,417,096, incorporated herein by reference. The cables are routed to local access points within the building which require the power.
In such undercarpet power systems, the power is available through floor mounted duplex receptacles included within the system and are interconnected to the flat undercarpet power cable. The duplex receptacle includes power contacts on an underside of the housing which pierce through the insulation of the flat undercarpet cable to make contact with the conductors of the power cable. The upper face of the housing includes a mating face or receptacle for the acceptance of a standard three prong plug carrying hot, neutral and ground contacts. A flat metallic ground plane is then placed over the top of the flat undercarpet cable which is used as a ground plane for the system but also mechanically protects the undercarpet power system from the atmosphere above the cable.
An advantage of such a system is found in the replacement and/or ease of changing electrical requirements within the building due to relocation or changing power requirements. It should be appreciated that the carpet squares can merely be uplifted for accessing the power cable, and further cable sections can be added or rerouted to other areas of the building where the power is needed. The shortcoming of this system is that during the rewiring of an office, the carpeting must be uplifted for some distance for the maintenance personnel and electricians to work on the system. Also this system can be quite labor intensive in that the new wire must now be spliced into the old, or the old wire rerouted to a new location with the preparation of the floor, cabling and ground as mentioned before.
The second system is similar in concept to the undercarpet system, but the second system is premised on the fact that the floor is actually elevated from the sub-base or structural portion of the building. In the construction of such a building, the concrete base would be poured, which defines the support structure, while the working floor would be built up from the concrete floor on "stilts" or pedestals. The floor would be laid in sections with each section being installed within a separate divided compartment within the frame structure. Each of the floor sections would be fairly stout, usually a 2 foot by 2 foot, one inch thick metal plate, which is capable of acting as a load bearing member.
Since the floor is elevated from the structural base, the void beneath the working floor is usable for such uses as wiring of power, phone, data lines, plumbing and the like. With this void beneath the working floor, the size of the cable and the accessories therefore are not as critical in the case of the undercarpet power system. However, the power systems must still meet such safety standards as U.L., NEMA, and various other local standards which may be placed upon the building contractors and electrical equipment manufacturers.
For this reason, such wiring systems typically use standard power cable within a conduit where the conduit and wiring terminates at some point away from the junction box, in other words the power cabling is "hard wired". Present electrical systems include standard power cable which is electrically connected to power receptacles, and the like, at the base of the floor. When this type of electrical connection is made, that is, when an electrical connection must be made in the customer's facility, according to U.L. and NEC standards these products are "unfinished products" and must be installed within a junction box. These same standards set a volumetric requirement which must be maintained for the floor mounted junction boxes. These junction boxes are presently used in the field of elevated floor construction with the junction boxes located within the periphery of one of the thick metal plates of the floor.
The use of such large junction boxes first causes for a complementary sized hole to be installed within or through the floor panel. Moreover, the existing systems require, once this large box is installed, the installation and electrical connection of the electrical splices or electrical receptacles within the junction box. Often times, the location of the desired electrical outlets is changed, as offices or secretarial staff is relocated within a building and the system must again be rewired. The junction box could be removed from the floor plate along with the related electrical hardware therein, although in all likelihood, when the cost of labor is considered, economy would probably dictate to simply leave the original box in the floor and reinstall a new box in a different floor panel.
In the third system, several stories within a particular building include concrete floors with drop ceilings beneath the floor for the room below. Holes are drilled through the concrete and "poke through" type wiring devices are inserted through the holes. These devices include a cylindrical tube which projects into the hole and extends beyond the underside of the concrete floor which places the end in the area above the drop ceiling in the floor below, thus access to the tube can be made by removing the ceiling tiles from the underside. The end of the tube includes electrical connections for use with flexible wiring interconnections. The opposite end of the tube includes fixturing for the mounting of duplex receptacles. However, the mounting plate is within the confines of the upper box which makes the box an open system, and requires an electrician for installation. These systems also require a heat expansion ring extending around the cylindrical tube to prevent the spreading of fires from one floor to the other. In the event of a fire the heat generated within the confines of the floor on fire, causes the fire retardant ring to expand and seal the opening through which the cylindrical tube extends.